Catacombs of Rome (English Wikipedia)

Heiken, Grant; Funiciello, Renato; and de Rita, Donatella (2005). The Seven Hills of Rome: A Geological Tour of the Eternal City. Princeton University Press (published 2013). p. 42. ISBN 9781400849376. Retrieved 2016-01-31. Underground Roman stone quarries and catacombs were excavated, mostly in tufa deposits, in and around Rome.

catacombe.org

"Catacombe San Sebastiano". catacombe.org. Archived from the original on 2012-07-23. Retrieved 2021-10-31.

Rutgers, L.V.; van Strydonck, M.; Boudin, M.; van der Linde, C. (May 2009). "Stable isotope data from the early Christian catacombs of ancient Rome: new insights into the dietary habits of Rome's early Christians". Journal of Archaeological Science. 36 (5): 1127–1134. Bibcode:2009JArSc..36.1127R. doi:10.1016/j.jas.2008.12.015.
Robertson, R. Reid (November 1933). "The Christian Catacombs of Rome". The Expository Times. 45 (2): 90–94. doi:10.1177/001452463304500208. S2CID 170579130.
Osborne, J. (1985). "The Roman Catacombs in the Middle Ages". Papers of the British School at Rome. 53: 278–328. doi:10.1017/S0068246200011569. ISSN 0068-2462. JSTOR 40310821. S2CID 163223163.

Rutgers, L.V.; van Strydonck, M.; Boudin, M.; van der Linde, C. (May 2009). "Stable isotope data from the early Christian catacombs of ancient Rome: new insights into the dietary habits of Rome's early Christians". Journal of Archaeological Science. 36 (5): 1127–1134. Bibcode:2009JArSc..36.1127R. doi:10.1016/j.jas.2008.12.015.

Robertson, R. Reid (November 1933). "The Christian Catacombs of Rome". The Expository Times. 45 (2): 90–94. doi:10.1177/001452463304500208. S2CID 170579130.
Osborne, J. (1985). "The Roman Catacombs in the Middle Ages". Papers of the British School at Rome. 53: 278–328. doi:10.1017/S0068246200011569. ISSN 0068-2462. JSTOR 40310821. S2CID 163223163.

"Rome's Ancient Catacombs". National Geographic Society. 21 January 2017. Archived from the original on March 6, 2021.
White, L. Michael. "In The Catacombs | From Jesus To Christ - The First Christians | FRONTLINE". PBS. Archived from the original on 1999-11-11. Retrieved 2021-07-14.
"Jewish and Christian Catacombs in Rome". bibleodyssey.org. Archived from the original on 2021-09-15. Retrieved 2021-09-15.
"Catacombe San Sebastiano". catacombe.org. Archived from the original on 2012-07-23. Retrieved 2021-10-31.

Flinn, Frank K. (2007). "catacombs". Encyclopedia of Catholicism. Facts on File. p. 133. ISBN 978-0-8160-7565-2. OCLC 882540074.
Osborne, J. (1985). "The Roman Catacombs in the Middle Ages". Papers of the British School at Rome. 53: 278–328. doi:10.1017/S0068246200011569. ISSN 0068-2462. JSTOR 40310821. S2CID 163223163.